Study Suggests Baby Brains Tune In to Familiar Faces

Although six-month-old babies are quite helpless in a
lot of ways, it seems that they can outperform their
older caretakers in at least one respect: distinguishing
among faces of other species. Whereas adults can
easily tell human faces apart but lack a similar ability to
discern nonhuman primate visages, six-month-olds can
recognize familiar faces of both humans and monkeys,
according to a study published today in the journal
Science.

Charles A. Nelson of the University of Minnesota
hypothesized that as infants gain experience seeing
faces, their brains tune in to the types of faces they see
most often and become less receptive to those they see
less regularly. If this is the case, the theory goes,
younger infantswho have had less time to become
adept at discriminating among human facesshould be
better at differentiating among faces of other species.
When Nelson and his colleagues Michelle de Hann of
University College London and Olivier Pascalis of the University of Sheffield tested the reactions of
six-month-olds, nine-month-olds and adults to color photographs of people and monkeys (see
image), they observed exactly this. The researchers videotaped the subjects while showing them a
unique human or primate face together with a previously viewed image. The team found that adults
took longer to examine a novel human face compared with a previously viewed one but spent a similar
amount of time examining both monkey pictures. The nine-month-olds demonstrated the same
pattern. The six-month-olds, in contrast, spent significantly less time looking at pictures they had seen
before than they did inspecting new photos for both species, which suggests they can discriminate
between monkeys as well as humans. "We usually think about development as a process of gaining
skills, so what is surprising about this case is that babies seem to be losing ability with age," de Hann
says. "This is probably a reflection of the brain's 'tuning in' to the perceptual differences that are most
important for telling human faces apart, and losing the ability to detect those differences that are not so
useful."

Although it is still possible for humans to learn to recognize different faces of another species, the
results indicate that the face-processing system for adults has a preferred human template. The fact
that infants lose the ability to perceive facial differences, dubbed perceptual narrowing, may signal a
general change in neural networks involved in early cognition, Nelson says. "We're interested in what
this means in neurological terms," he adds. "For example, we don't know why this particular area of
the brainthe fusiform gyrusgets the assignment of distinguishing faces."

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